A PR can change a package's directory without bumping its version: an
upstream hook, its tests, a README. bin/build then plans nothing, and
the pack step failed on the empty build output, turning the required
result check red (seen on #769). Make the same dry-run check
publish.yml's rebuild job already makes, and skip packing and uploading
when nothing was built. publish.yml finds no artifact for such a merge
and records the package as already published.
Emir Beganovic
5bd85a785f